# [Equest-users] Reply： The problem of minimum equipment efficiency requirement of Ashrae 90.1-2007

Jones, Christopher cjones at halsall.com
Wed May 27 11:40:16 PDT 2015

```Hello Nick,
Do you also have a handy conversion between Et and Ec?

Thanks for your assistance!

Christopher Jones, P.Eng.
Tel: 416.644.4226 • Toll Free: 1.888.425.7255 x 527

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Nicholas Caton
Sent: Friday, May 29, 2015 11:17 AM
To: 赵永青; Equest-users
Subject: Re: [Equest-users] 回复：RE: 回复： 回复：RE: Reply： The problem of minimum equipment efficiency requirement of Ashrae 90.1-2007

Yeah same for my case (not AFUE), though that’s good thinking!

When I do have an AFUE boiler requirement, I have found it easier to stick with the default library curves / standby inputs & to determine the full load HIR with the following equations:

HIR = f(AFUE):   [Reference: California Energy Commission's 2005 "Nonresidential Alternative Calculation Method (ACM) Approval Manual"]
For single packaged central furnace (baseline system #3):                            HIR = (.005163*AFUE+0.4033)^-1
For Boilers where 75 ≤ AFUE < 80 (Baseline systems #1, #5 &#7):               HIR = (0.1*AFUE+72.5)^-1*100
For Boilers where 80 ≤ AFUE < 100 (Baseline systems #1, #5 &#7):            HIR = (0.875*AFUE+10.5)^-1*100

For completeness, here are the other equations I keep handy for converting other seasonal efficiencies to steady-state inputs:

EER=f(SEER):      [Reference: NREL Building America House Simulation Protocol (Revised), citing Wassmer, M. (2003). A Component-Based Model for Residential Air Conditioner and Heat Pump Energy Calculations.]
(AC) (Baseline Systems #1, #3, #5 & #6):               EERNET= -0.0182*SEER^2 + 1.1088*SEER
(HP-cooling) (Baseline Systems #2 & #4):              EERNET = -0.02*SEER^2 + 1.1268*SEER

COP=f(HSPF):    [Reference: Wassmer, M. (2003). A Component-Based Model for Residential Air Conditioner and Heat Pump Energy Calculations. Masters Thesis, University of Colorado at Boulder.]
(HP-heating) (Baseline Systems #2 & #4):             COPNET = -0.0255*HSPF^2 + 0.6239*HSPF

IIRC, each of the above cited references determines these equations based on a survey of real-world equipment from various manufacturers in order to plot a quadratic trendline.  That trendline establishes the relationship between steady state full load efficiency and the associated seasonal efficiency rating.  In time (or until such equations are added to Appendix G to regulate how modelers approach seasonal efficiency requirements), it may be appropriate to seek out similar research to update these equations every so often, but for the present and past couple of years I have had zero problems using this family of equations for my LEED reviews.

~Nick

NICK CATON, P.E.
Owner

Caton Energy Consulting
1150 N. 192nd St., #4-202
Shoreline, WA 98133
office:  785.410.3317
www.catonenergy.com

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>] On Behalf Of ???
Sent: Monday, May 25, 2015 6:24 AM
To: Equest-users
Subject: [Equest-users] 回复：RE: 回复： 回复：RE: Reply： The problem of minimum equipment efficiency requirement of Ashrae 90.1-2007

I also find the  definition of AFUE in manual , but the boiler capacity of my project( a very big project) is larger than 88kW, So the efficiency of boiler should be 80%(Ec),not 80%(AFUE).

------------------
Yongqing Zhao
Changsha Green Building & Energy Saving Technology CO.,LTD
Telephone:13574805636
Email:zhaoyongqing1987 at 126.com<mailto:Email%3Azhaoyongqing1987 at 126.com>
503271081 at qq.com<mailto:503271081 at qq.com>

------------------ 原始邮件 ------------------

I agree with Nick that removing the default start-up times in the baseline seems inappropriate and that it should also be done in the proposed design if done in the reference (when the baseline performance is based on Et)

I didn’t see any model attached so I couldn’t check but could it be possible the boiler size falls into the smaller category of table 6.8.1F where it’s efficiency is defined as 80% AFUE? The comment of the reviewer would make much more sense if it was the case, since 80% AFUE is different from 80% Et. In my understanding, 80% AFUE refers to a global annual efficiency of 80% and 80% Et refers to 80% efficiency at peak load which would result in a global annual efficiency lower than 80% when you consider part loads and boiler cycling.

I would deem as correct the reviewer’s comment if the boiler size falls into the 80% AFUE category.

“The AFUE differs from the true 'thermal efficiency' in that it is not a steady-state, peak measure of conversion efficiency, but instead attempts to represent the actual, season-long, average efficiency of that piece of equipment, including the operating transients.[1] “
1^ Systems and Equipment volume of the ASHRAE Handbook, ASHRAE, Inc., Atlanta, GA, USA, 2004

However, if your boiler size falls into the Et or Ec  category then, as everyone else here, I find the comment somewhat strange.

[cid:image001.jpg at 01D0988B.0B5C0340]

Patrick Lapierre_ing.
plapierre at bpa.ca<mailto:plapierre at bpa.ca>

De : Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] De la part de ???
Envoyé : 24 mai 2015 20:42
À : Daniel Knapp; Nicholas Caton
Cc : equest-users at lists.onebuilding<mailto:equest-users at lists.onebuilding>
Objet : [Equest-users] 回复： 回复：RE: Reply： The problem of minimum equipment efficiency requirement of Ashrae 90.1-2007

Hi,Dan

The comment is a full version,no context missing!I  also feel very strange with it.

------------------
Yongqing Zhao
Changsha Green Building & Energy Saving Technology CO.,LTD
Telephone:13574805636
Email:zhaoyongqing1987 at 126.com<mailto:Email%3Azhaoyongqing1987 at 126.com>
503271081 at qq.com<mailto:503271081 at qq.com>

------------------ 原始邮件 ------------------

I'm with Nick. I find the GBCI reviewer comment as reported to be a bit strange and I wonder if there is some context missing. Is it possible that the seasonal efficiency was much lower than 80% in the baseline, suggesting either oversizing of the baseline boilers or a curve that is different from the proposed curve?

Best,
Dan

—
Sent from my phone

On May 24, 2015, at 11:38 AM, Nicholas Caton <ncaton at catonenergy.com<mailto:ncaton at catonenergy.com>> wrote:
I’m happy you are arriving at the same result, however to be clear I do not think the reviewer is correct to assert the prescribed efficiency is anything other than the full-load efficiency.

Follow the cited Test Procedure CFR 431 led me to:
https://www.law.cornell.edu/cfr/text/10/431.86

“§ 431.86 (c) (3) (ii) Thermal Efficiency. Use the calculation procedure for the thermal efficiency test specified in Section 11.1 of the HI BTS-2000, Rev 06.07 (incorporated by reference, see§ 431.85).”

I then found the referenced HI standard here (PDF link): https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CB8QFjAA&url=https%3A%2F%2Flaw.resource.org%2Fpub%2Fus%2Fcfr%2Fibr%2F004%2Fhi.BTS-2000.2007.pdf&ei=R-dhVZr3FoffoASKxYC4Bw&usg=AFQjCNGb2HahzcO_Q-BftBzCugY5sPtifg&sig2=k1fojL9GcpjnN6T2fdzOug

In that standard, section 5 reads:
5.0  TYPES OF TESTS
5.1 Thermal Efficiency Test
Shall consist of a test point conducted at 100% ± 2% of the nameplate boiler input. The test shall
yield a complete accounting of the energy input in terms of output and losses.
5.2 Combustion Efficiency Test
Shall consist of a test point conducted at 100% ± 2% of the input to the boiler and shall yield an
accounting of energy input in terms of products of combustion only.

From this, it is clear Et and Ec as prescribed by 90.1 are only the efficiencies as measured at full load.  The test procedures following under section 9 deliberately exclude the effects of warmup/standby (equipment is made to warm up and arrive at the mandated operating conditions prior to measurements).

Section 11.1 of the standard prescribes all the calculations required, including Et = 100*QOUT / QIN , however the preceding sections makes clear we are in no way standardizing part load performance or warmup/standby performance.

Rounding back to 90.1… section 6.4.1.1 further cements the notion (“packaged boilers” fall under 1992 EPACT):
[cid:image002.png at 01D0988B.0B5C0340]

All this reinforces the point that 90.1 simply does not prescribe part load performance for baseline boilers.  To perform a simulation in compliance with Appendix G the onus is upon the energy modeler to make reasonable, defensible assumptions on that front.  I don’t see how forcing full-load efficiencies at all part-load conditions and removing standby/startup operation energies is more reasonable or reflects reality better than the defaults.

If this is a new GBCI position they plan to hard-line on, then I would speculate it would be equally fair (albeit far more unrealistic for condensing cases) to give your proposed boilers the same treatment… extra work for a step backwards from reality…?

Thoughts?

~Nick

NICK CATON, P.E.
Owner

Caton Energy Consulting
1150 N. 192nd St., #4-202
Shoreline, WA 98133
office:  785.410.3317
www.catonenergy.com<http://www.catonenergy.com>

From: 冷面寒枪 [mailto:zhaoyongqing1987 at qq.com<mailto:zhaoyongqing1987 at qq.com>]
Sent: Sunday, May 24, 2015 7:13 AM
To: Nicholas Caton; Julien Marrec
Cc: equest-users at lists.onebuilding<mailto:equest-users at lists.onebuilding>
Subject: 回复：RE: [Equest-users] Reply： The problem of minimum equipment efficiency requirement of Ashrae 90.1-2007

Hi,Nick

Than you for your insight!

Except default curve and start up time, Min-Ratio also will result in discrepancy between annual equivalent HIR and nominal HIR. After I revised curve ,set start-time and Min-Ratio to 0,and hourly report and PS-C report indicate that the annual equivalent HIR  is accord with nominal HIR

------------------
Yongqing Zhao
Changsha Green Building & Energy Saving Technology CO.,LTD
Telephone:13574805636
Email:zhaoyongqing1987 at 126.com<mailto:Email%3Azhaoyongqing1987 at 126.com>
503271081 at qq.com<mailto:503271081 at qq.com>

------------------ 原始邮件 ------------------

I received some similar review language very recently suggesting 80% efficiency is expected at all/most part load conditions for the baseline boiler….  Similar context in that case with the boiler rarely operating near full load.

My comment has other issues that would cloud the topic at-hand, but here is  truncated version:

“…Furthermore, the average boiler efficiencies in the Baseline PS-C output reports, calculated by dividing the boiler energy consumption by the annual boiler heating energy generated was… [approximately 5% lower than the nominal efficiency input & documented]. Revise the baseline boiler efficiency to 80% and revise the boiler curve for the Baseline case as necessary to have an average efficiency that is near 80%. Provide updated PS-C reports for the Baseline confirming that the average baseline efficiency is near 80%.”

This is the first time I have run into commentary checking up on PS-C’s output at all, and I’m using the same library curves as always for typical baseline boilers.

I believe the PS-C discrepancy is explained both by the non-flat library curve and by the boiler’s default start-up loads, in combination.

Here is the default library curve – it is (roughly, but not quite) linear:
<image002.png>
<image003.png>

[For those unfamiliar, the Y-axis is a unitless multiplier]

If I’m not mistaken, this curve serves double-duty:  it simultaneously applies the hourly PLR to the full capacity (as either input or auto-sized) and also accounts for increased HIR (lower efficiency) as the PLR drops.  My understanding in equation form:
Energy Consumed (for the hour) = (Boiler full capacity as input/autosized) * (Boiler nominal HIR input @ full load) * HIRf(PLR)

If all of that is true, a perfectly “flat efficiency” curve, returning your nominal input HIR at all efficiencies, would therefore be Z = X.  That’s plotted above for reference with a light/thin line.

Even with such a “flat efficiency” curve applied to a test-case, PS-C’s outputs still suggest an annual equivalent HIR higher than the nominal input.  Zeroing out the startup/standby inputs as well is required to get PS-C to report your nominal HIR = annual fuel / annual load:
[cid:image003.png at 01D0988B.0B5C0340]

I think the correct response (which perhaps I’ve mostly composed above) is to demonstrate the causes (library curve shape, startup/standby defaults), and to assert these are all appropriately applied to the baseline boiler, though none of this is regulated by 90.1 to the best of my knowledge so it might be relatively shaky territory.

I would wager 90% of all eQuest baseline boilers submitted to GBCI to date probably don’t mess with the library curves or standby/startup inputs, but that’s pure speculation on my part.

Has anybody ever tried to explain/justify the default boiler curve and default startup/standby inputs?  Do we know where those defaults come from?

~Nick

NICK CATON, P.E.
Owner

Caton Energy Consulting
1150 N. 192nd St., #4-202
Shoreline, WA 98133
office:  785.410.3317
www.catonenergy.com<http://www.catonenergy.com/>

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>] On Behalf Of ???
Sent: Sunday, May 24, 2015 5:34 AM
To: Julien Marrec
Cc: equest-users at lists.onebuilding<mailto:equest-users at lists.onebuilding>
Subject: [Equest-users] Reply： The problem of minimum equipment efficiency requirement of Ashrae 90.1-2007

Hi,Julien

I understand his meaning is keep a constant efficiency and I know the flat efficiency in equest is a curve that is y=x, but I can't  confirm if a constant efficiency is Ashrae 90.1-2007's original intent.

------------------
Yongqing Zhao
Changsha Green Building & Energy Saving Technology CO.,LTD
Telephone:13574805636
Email:zhaoyongqing1987 at 126.com<mailto:Email%3Azhaoyongqing1987 at 126.com>
503271081 at qq.com<mailto:503271081 at qq.com>

------------------ 原始邮件 ------------------

Hey,

He's saying that you need to make sure that the curve boiler-fPLR gives you a constant efficiency. As far as I remember, the default atmospheric curve from equest is like this.
Don't be confused by "flat". A flat efficiency curve is when you plot efficiency=f(PLR). In equest, it should be a curve that is y=x

Look at the curve you used.

Best,
Julien

Envoyé de mon iPhone

Le 24 mai 2015 à 11:27, "赵永青" <503271081 at qq.com<mailto:503271081 at qq.com>> a écrit :
I get the energy model comments from LEED reviewer as following:

The narrative response indicates that the Baseline boiler has been modeled utilizing operating performance curves and a boiler HIR of 1.25. However, since the boiler operation HIR is based on the performance curves, the HIR is less than 1.25 in the part-load condition, which is inappropriate. Revise the Baseline boilers to include a flat efficiency of 80% for all part-loads. Provide eQuest input files or screen shots verifying the boiler efficiency has been modeled as required.
However, I can not understand it very much. The minimum equipment efficiency requirement(80 % Et) of Ashrae 90.1-2007 should be base on full load condition.Why the LEED reviewer raise such a question?Any insight is appreciate!!

Thanks
------------------
Yongqing Zhao
Changsha Green Building & Energy Saving Technology CO.,LTD
Telephone:13574805636
Email:zhaoyongqing1987 at 126.com<http://126.com/>
503271081 at qq.com<mailto:503271081 at qq.com>

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